To provide a mental resources assessment device which makes calculations and assessments of a driver's mental resources, that is, a newly proposed general idea indicating an index of the probability of making a manmade error by the driver in driving, based on a biological indicator of the driver, and its utilization.

This mental resources assessment device, designed to accurately assess the probability of a driver's making a manmade error leading to a traffic accident, is provided with a measuring means for measuring the hygienic indicator of the driver of a vehicle, a notifying means for detecting the positional information of the vehicle as well as the traffic information and then notifying it, a mental resources calculating means for calculating the mental resources of the driver based on his/her hygienic indicator when the vehicle is on a prescribed traffic condition, using the information from the measuring means and the notifying means mentioned above, and a judging means for judging whether or not the mental resources of the driver lie within a prescribed range.